1. Field of Invention:
The present invention relates to insulating and sealing rings for ladle preheaters.
2. Description of the Prior Art
Refractory ceramic fiber modules are becoming increasingly more common as insulative seals on ladle preheaters to seal against the ladle rim during preheating. U.S. Pat. No. 4,364,729 and U.S. Pat. No. 4,229,211 were examples of this type of ladle preheater seals formed of refractory ceramic fiber modules. In these systems, substantially the entire rectangular support frame or plate was covered with refractory ceramic fiber modules, such as those according to U.S. Pat. No. 4,001,996. These modules, typically having square prismic shape, were installed in a uniform grid pattern. Since the ladle rim was usually of circular or oval construction, the modules in the outer corners of the frame served no useful function other than support for the modules which did lie within the seal area. Establishing a circular or oval seal area with a uniform square grid pattern thus involved the use of inactive modules, which increased the cost of construction and maintenance.
U.S. Pat. No. 4,223,873, commonly owned with U.S. Pat. Nos. 4,364,729 and 4,229,211, was directed to a ladle preheater with a circular seal of compaction material. However, no structural details of this seal, or how it was to be installed and supported, were given. The rectangular ceramic fiber modules used for furnace wall insulation, such as those of U.S. Pat. No. 4,001,996 mentioned above, and others on the market did not lend themselves to forming circular seals. There were several ways that attempts could have been made to use them, but none were satisfactory. These square or rectangular modules could have been cut to fit a circular or oval seal pattern. This would have caused material waste and increased installation costs. Even more importantly, the structural integrity, and thus the compressive effects between adjacent modules, would be reduced. Alternatively, these modules could be arranged about a generally circular pattern, leaving gaps in spaces between adjacent rectangular modules where curved surfaces were necessary. This would require stuffing to be inserted in the spaces, increasing installation costs and resulting in irregular compressive effects.
Further, it would have been desirable in ladle preheaters of an earlier type, using refractory brick as a primary refractory between the ladle and the preheater, to obtain the benefits of refractory ceramic fiber insulation in the seal. However, the removal of the refractory brick and its replacement with rectangular fiber module systems of U.S. Pat. Nos. 4,364,729 and 4,229,211 would have required a complete retrofit, necessitating that the preheater be taken out of service for some considerable time.
Another problem common to both ceramic fiber and brick linings was caused by slag accumulating on the ladle rims in service. Due to the slag, the lining was often damaged in use, usually severely, requiring replacement. Until completion of replacement of damaged portions of the lining, the preheater had to be taken out of service. If repairs of the linings were not made, the steel shell of the preheater was subject to damage.